House-broken animals, such as cats, are trained into the habit of urinating and defecating in a specially provided litter box. Similarly, untrained and caged animals, such as guinea pigs, urinate and defecate on the floor of their cage, often in approximately the same floor area of the cage. Consequently, pet owners, homeowners, veterinarians and laboratory personnel have added absorbent materials to the litter box or cage to collect the urine and feces. After a relatively short period of time, the dross-soiled absorbent emits objectionable odors because of the presence of the urine and fecal matter.
In order to reduce or eliminate these objectionable odors, homeowners periodically remove the fecal matter from the litter absorbent physically. However, physical removal of the feces does not reduce or eliminate odors caused by the urine absorbed into the absorbent. Therefore, when the odors caused by the absorbed urine become intolerable, the homeowner discards the litter box absorbent material entirely. The homeowner then washes the litter box and refills the litter box with fresh litter box absorbent material. These activities are unpleasant, time-consuming and expensive. Consequently, the litter box absorbent material usually is a relatively inexpensive solid absorbent material, such that an individual cleaning of the litter box is not particularly economically burdensome. However, repeated litter box cleanings over a period of time accounts for relatively large expenditures.
The most commonly used litter box absorbent materials are inexpensive clays, such as calcined clays, that are safe and non-irritating to the animals, and that absorb relatively substantial amounts of liquids. Other porous, solid litter box absorbent materials that are used alone or in combination include straw, sawdust, wood chips, wood shavings, porous polymeric beads, shredded paper, sand, bark, cloth, ground corn husks, cellulose, and water-insoluble inorganic salts, such as calcium sulfate. Each of these absorbent materials has the advantage of low cost, but each suffers from the disadvantage of merely absorbing a liquid waste product and holding the product within its porous matrices, or, in the case of sand, absorbing the liquid dross on its surface. For each absorbent material, offensive odors are eventually caused by the absorbed urine, and the entire contents of the litter box, including soiled absorbent material and unsoiled absorbent material, has to be discarded.
Unicharm KK Japanese application J63044-822-A discloses a clay pet litter containing an organic acid and its salt as a deodorant. The clay litter of the present invention is natural clay, as mined and ground, that is extruded and, with or without an added adhesive, functions to agglomerate liquid animal dross for effective removal of the used liquid-soaked litter without organic acids or deodorant treatment.
Kenkyu Japanese application J6 1119-127-A discloses spraying a cyanoacrylic acid alkyl ester film on the surface of pet feces for removal of the feces separately from the litter.
Crampton et al. U.S. Pat. No. 4,657,881 teaches a pet litter formed from compacted fines of a non-swelling clay, e.g., calcium bentonite clay or other clays such that after compaction, the clay particles have a size of 710 microns to 4 millimeters. The Crampton patent teaches that a small percentage of additive (less than 10% by weight of the compacted particles, preferably less than 5%), such as a water-swellable clay, carboxymethyl cellulose or a soluble polysaccharide increases the absorbency of the litter composition. The Crampton patent does not disclose that the composition forms removable clumps when wetted with animal dross.
Other clumping animal litter compositions are described in this Assignee's U.S. Pat. Nos. 5,000,115 (Reissued as U.S. Pat. No. Re. 33 983); 5,129,365; and in pending U.S. application Ser. No. 07/880,580 filed May 8, 1992. These patents teach that a water-swellable bentonite clay particles, e.g., natural or synthetic sodium bentonite clay particles, will agglomerate with surrounding wetted sodium bentonite particles, when wetted with animal dross, to form a strong, cohesive clump that can be essentially completely removed from a litter box leaving essentially only unsoiled litter particles.
Stuart, in U.S. Pat. No. 4,685,420, discloses an improved litter box absorbent composition comprising from 0.01% to 5.0% by weight of a water-absorbent polymer, e.g., a polyacrylate in combination with a common litter box absorbent material. According to the method and composition of Stuart, the polyacrylate and absorbent material absorb the urine or similar waste material, and the polyacrylate interacts with the soiled litter box absorbent material to form a gelled product. Stuart teaches that the gelled absorbent material or clump then can be physically removed from the litter box to reduce the generation of offensive odors, and to avoid discarding the unsoiled portion of the absorbent material. However, the method and composition of Stuart suffers from the disadvantage of relative cost ineffectiveness. The commonly used litter box absorbent materials are very inexpensive materials, whereas the water-absorbent polymers of Stuart are relatively expensive products that can raise the initial cost of the litter box absorbent material to an unacceptable level in a very cost competitive market.
Others have attempted to provide an animal litter that forms strong, coherent clumps when wetted with animal dross by mixing the absorbent litter material with a dry, particulate water-soluble adhesive that is relatively inexpensive, such as a cellulosic adhesive, wheat paste (a pre-gelatinized starch), gums and the like. Examples of this expedient for manufacturing an animal litter, wherein the strength of the clump formed depends upon the addition of an adhesive, are the Buschur U.S. Pat. No. 5,176,107 and the Sowle U.S. Pat. No. 5,014,650. While each of these patents teach that clumps are formed with the addition of at least about 0.1% by weight of the water-soluble adhesive, it is clear from the examples disclosed in these patents coherent clumps, that do not suffer significantly from soiled particles spalling off of the clump before or during the clump removal process, are only achieved with the addition of at least about 0.5% by weight of the water-soluble adhesive.
In the cost conscious animal litter market, there has been a long-felt need to provide an animal litter manufactured from one or more very inexpensive components that, when wetted with animal dross, forms a strong, coherent clump, wherein soiled portions of the clump do not fall off of the clump for admixture with the unsoiled particles, in order to provide an animal litter composition that is essentially odor-free for an indefinite time period without completely replacing the contents of an animal litter box.